Cleanup inside IncomingVideoStream.

Removes logging, thread annotates members (finding 2 bugs where
variables were not protected by the correct critsect) and adds consts
and scoped_ptrs.

BUG=
R=mflodman@webrtc.org, stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/43219004

Cr-Commit-Position: refs/heads/master@{#9078}
4 files changed